Development of ovaries, allometry of reproductive traits and fecundity of Episyrphus balteatus (Diptera : Syrphidae)

Episyrphus balteatus only matures eggs after emergence. Ovaries develop in 4 stages. In the absence of oviposition sites, females refrain from oviposi ting and their ovaries progressively fill the abdomen and then egg resorpti on occurs. The potential fecundity, which is expressed by the ovariole numb er, the reproductive biomass and the abdomen volume, scales isometrically w ith the size of females. Egg size is much less variable and does not rise p roportionally to body size. In laboratory conditions, females of E. balteat us might lay between 2,000 and 4,500 eggs during their life-time at a rate of 1 to 2 eggs per ovariole per day. Both lifetime fecundity and rate of eg g production are directly related to the size of females. The potential and realized fecundities are likely to be limited by the availability of food resources during larval and adult life, respectively.